Do you mean Lawless Wasteland?

Yes, it's a terrible system and everyone hates it. You need to enslave the population as quickly as you can.

Okay, so how do I do that when the second I own the majority of the province and control switches, it goes unclaimed and all my troops are now unable to attack or move properly anymore? Why even do that anyway, because all I can see it doing is cause the player to stop everything, spend power points to retake the province, and then have to un-♥♥♥♥ all the battle lines... while the AI instantly counter attacks. It only feels like a nerf to the player, and a sloppy and heavy handed one at that.

If someone could explain WHY the system exists in the first place, then I might gain a slight shred of sympathy for the dev/devs. At this point, im just sharpening a pitchfork to join the mob to get this awful thing removed from an otherwise great mod.

It was part of the update after the main game introduced the current resistance system. I suppose that the mod maker was thinking something along the lines of 'how would Purists handle unruly mutants?'.

Well, increased resistance in conquered territory, decisions to wipe out mutants and therefore reduce population in those zones to reduce resistance or advance compliance in those zones, or gain a national idea that increases the debuff received proportional to the amount of non pacified territory, having the territory go unclaimed AFTER a war if decision or PP wasn't spent to keep a hold of them...

You know, anything along the lines of dealing with resistance instead of having entire states just up and go unclaimed.

My own thoughts were that if the Purist focus ever got reworked was that they could get a choice between enslave the wastelanders and exterminating them and replacing them with clones.